- One of the 13 essential elements for plant growth and is one of the 6 Major Elements, based on concentration required
- amount required for healthy plant growth: 14,000 ppm, 1.4%, dry soil matter
- Principle form of uptake: ionic forms ammonium, (NH4+) and nitrate (NO3–)
- the preferred form changes from NH4 to NO3 as the plant approaches maturity
- Nitrate moves through the soil primarily by mass flow, but also by diffusion
- soil conditions related to deficiency of nitrogen:
- sandy soils leached by heavy rainfall or irrigation
- mineral soils low in organic matter
- long history of crop depleting because not enough N added
- soil factors that affect plant uptake:
- Temperature
- the level of decomposition of organic matter
- plowing under highly carbonaceous materials (cover crops or straw) when still being decomposed by soil organisms will reduce available N, since microorganisms are better competitors than plants for resources
- plant factors that affect uptake of nitrogen:
- hybrid or variety of plant
- stage of growth
- interactions among the other elements
- molybdenum is required for converting nitrate to nitrogen – if the form of nitrogen supplied to the plant is NH4, then the amount of molybdenum required is greatly reduced
Nitrogen functions in plant:
- combines with carbohydrates and sometimes sulfur to form amino acids, amino enzymes, chlorophyll, alkaloids, nucleic acids, and purine bases
Sources for Nitrogen:
- organic debris, plant residues, and microorganisms are the major sources of nitrogen
Nitrogen Deficiency Symptoms:
- pale yellow-green leaves (can be confused with sulfur deficiency)
- Nitrogen is very mobile within the plant, so deficiency symptoms will first show in the older leaves, since the plant is moving N from older leaves to newer growth to supply growing points
- Nitrogen content in leaves naturally declines with maturity of the plant, so some symptoms of deficiency are normal in those older leaves, as the plant ages
